A solution contains a mixture of substance A and substance B, both of which are volatile. The mole fraction of substance A is 0.35. At 32 °C the vapor pressure of pure A is 87 mmHg, and the vapor pressure of pure B is 122 mmHg. What is the total vapor pressure of the solution at this temperature?

a) 110 mmHg 

b) 209 mmHg

c) 99.3 mmHg 

d) 73.2 mmHg